1. Field of the Invention
The present invention relates to a method and apparatus for optical recording and image forming, and more particularly to a method and apparatus for optical recording and image forming capable of correcting a magnification error caused in a main scanning direction.
2. Discussion of the Background
In a background image forming apparatus using an optical scanning system, a typical process of image forming is conducted in a way such that a light beam is modulated and is reformed by a rotating deflecting member (e.g., a polygon mirror) into a scanning light beam which passes through an fθ lens and then impinges on an image carrying member (e.g., a photosensitive member). The scanning light beam deflected by the rotating deflecting member runs at a constant angular speed in a main scanning direction and is changed to the scanning light beam with a constant linear speed.
The background image forming apparatus, however, has a drawback in which an accuracy of an image magnification in a scanning line differs between apparatuses due to characteristics of optical components such as lenses used therein. Plastic lenses, in particular, are mostly susceptible to variations in environmental temperature and are easily deformed, resulting in a change in refractive index. This may cause a change in a scanning position of an image plane on a photosensitive member and accordingly an error of an image magnification in the main scanning direction. As a result, a high quality image is failed. The failure may become more serious in a color image forming apparatus which handles a plurality of different color images with using a plurality of laser beams and a plurality of lens systems. That is, the plurality of different color images may have errors independently which cause a typical color image problem called a color deviation. Therefore, the image magnifications of the different color images need to match with each other as much as possible.